Fig 2: DCX+ cells in postnatal streams are interneurons. (a,c,e) P20 DCX+ cells in each stream express GAD67, Sp8, and SCGN, respectively. (b) Quantification of DCX/GAD67 co‐localization in each stream. (d) Quantification of DCX/Sp8 co‐localization in each stream. (f) Quantification of DCX/SCGN co‐localization in each stream. (g) Individual clusters express DCX, Sp8, and SCGN. (h) Individual DCX+ cells express both Sp8 and SCGN. (i–l) DCX+ cells do not co‐localize with glial markers GFAP, OLIG2, SOX10, or IBA1. Scale bar (a–l) = 10 μm. Scale bar g = 50 μm [Color figure can be viewed at http://wileyonlinelibrary.com]

Fig 3: With iDISCO, SCGN+ cells appear to transition between white matter streams and cortex. (a) P20 ferret MMS SCGN+ cells are observed outside the MMS and are oriented toward the prefrontal cortex. (b) At P40, fewer SCGN+ cells are observed outside the MMS oriented toward the prefrontal cortex. (c) At P65, few SCGN+ cells are observed outside the MMS. (d,h) P20 iDISCO cleared sagittal and coronal sections stained with SCGN. (e–g,i–k) Higher resolution images focused on multitude of SCGN+ cells appearing to transition between the white matter streams and cortex. Scale bars a–c = 100 μm. Scale bar inset a = 10 μm. Scale bars d,h = 1 mm. Scale bars e–g,i–k = 100 μm [Color figure can be viewed at http://wileyonlinelibrary.com]

Fig 4: SCGN+ cells exist in the white matter into adulthood. (a) P65 white matter SCGN+ cells with mature morphology do not express DCX. (b) Quantification of number of SCGN+ cells with mature morphology from P20 to P90. (c) White matter SCGN+ cells with mature morphology co‐localize with calretinin. (d) Cleaved caspase 3 signal in the white matter does not co‐localize with SCGN. (e) Quantification of the number of caspase+ cells in the white matter from P20 to P65. Scale bars a,c,d = 20 μm [Color figure can be viewed at http://wileyonlinelibrary.com]

Fig 5: Cone-bipolar cells and synapses in outer plexiform layer. (A) Representative confocal images taken from the posterior pole (PP), equator (Eq), peripheral retina (PR) and marginal retina (MR) of naïve control eye staining for secretagogin+ (SCGN, green). Nuclei were stained with DAPI (blue). (B) SCGN+ cone-bipolar cells density expressed as % of PP in different retinal locations in naïve control, self-control and FDM eyes. (C) Representative confocal images of bassoon (red) and SCGN (green) labelled retinas from PP of naïve control, self-control and FDM eyes. Box 1 showing cone-bipolar dendrites; box 2 showing bassoon+ synaptic ribbon in the outer plexiform layer, box 3 showing SCGN+ cone-bipolar cell body. (D-F) Quantitative data of SCGN+ cone-bipolar dendrites (D), the number of SCGN+ cone-bipolar cells (E) and bassoon+ synaptic ribbons (F) in different retinal locations of naïve control, self-control and FDM eyes. INL, inner nuclear layer; ONL, outer nuclear layer. Scale Bar: 50 µm. Mean ± SD, n = 3~9/group. * p < 0.05. One-way ANOVA followed by Fisher’s LSD test.